The present invention relates to antennas and more particularly to single-feed multi-frequency multi-polarization antennas.
Antennas are in widespread use in automobiles, which typically include antennas for one or more of AM radio, FM radio, satellite radio, cellular phones, and GPS. These signals are of different frequencies and polarizations. For example, the signals associated with satellite radio (e.g. brand names XM® and Sirius®) are in the range of 2.320 to 2.345 GHz and are left-hand circularly polarized (LHCP); and the signals associated with global positioning systems (GPS) are in the range of 1.574 to 1.576 GHz and are right-hand circularly polarized (RHCP).
Antenna packages have been developed to receive and output multiple signals. At least one such package outputs the multiple signals on a single feed as disclosed in U.S. Pat. No. 7,164,385 issued Jan. 16, 2007 and U.S. Pat. No. 7,405,700 issued Jul. 29, 2008 both to Duzdar et al. As described in the patents, the disclosed antenna includes coplanar inner and outer patches. The outer patch surrounds the inner patch. The two patches are physically spaced from one another. A single feed is connected to the inner patch. The inner patch resonates at a first frequency with a first antenna polarization sense. The inner and outer patches together resonate at a second frequency with a second polarization sense. Both signals are outputted on the single feed.
Unfortunately, the prior art antenna has two shortcomings. First, the antenna is difficult to manufacture and to tune. While a consistent accurate gap between the antenna elements is important for the proper function of the antenna, current screening and printing processes do not provide the desired accuracy to produce antennas having a consistent accurate gap between the elements. Second, the two frequency bands cannot be tuned independently.